Hi I've just bought my first engine a Petter A1 with a belt driven generator. The engine looks to be in good condition, nothing a clean and fresh paint wouldn't fix, the only missing bits I can see are the bolts for the petrol tank, I'm assuming they are whitworth but I'm not sure on the exact thread, anyone know what I need?

The bolt threads on the Petter will be BSF Ian, probably 3/8th at a guess. Copper cored HT lead can normally be bought at motorfactors or lawn mower repairers by the metre, don't use the modern graphite cored lead though as that can give you problems. I see you live not far from me (Matlock).

Thanks for that, someone else mentioned 5\16 BSF on a Facebook group, I'll get a book ordered next week. I asked the guy who sold it me what the thread was but I don't think he understood imperial too well, or thread sizes at all. ( he stuck a 13mm socket on a bolt and told me 13mm)